This invention relates to machines for actuating railroad switches. Machines of this type are shown in U.S. Pat. Nos. 3,158,345 and 3,363,097. Generally, the actuating machines include an electric motor which drives a hydraulic pump. The pump supplies a hydraulic cylinder which is operatively connected to the railroad switch points. The switch machine of the present invention utilizes a rotary cam which is connected by a throw rod to the switch points. The cam is arranged to be rotated in opposite directions by successive extensions of the hydraulic piston rod. Thus, when the piston rod is extended it engages the rotary cam and causes the switch points to be thrown from an initial limit position to a second limit position. Then the piston rod is retracted, leaving the cam in a position where the next extension of the piston rod will cause the switch points to be moved from the second position back to the initial limit position. The rotary cam and its operation are described in U.S. Pat. Nos. 3,158,345 and 3,363,097.
Obviously, with the hydraulic cylinder and rotary cam arrangement described, some means must be provided for supplying hydraulic fluid such that the cylinder will go through its extension and retraction cycle. In U.S. Pat. No. 3,363,097 this is accomplished by providing a reversible electric motor and pump. The reversible motor eliminates the need for any hydraulic control valves but it has the disadvantage of requiring more complicated motor controls. Under U.S. Pat. No. 3,158,345 a three-position directional valve and an accumulator are utilized. The three-position valve has a center or neutral position where no fluid is supplied to the cylinder. It also has a left position wherein fluid is supplied to the piston side of the cylinder and a right position wherein fluid is supplied to the rod side of the cylinder. While both of these systems are operable, there is a certain amount of lost time involved in reversing the motor in the one case or shifting the positions of the directional valve, in the other case. The present invention is founded in a development which provides a high-speed switch machine which eliminates these time delays.